Made available in DSpace on 2016-06-02T19:38:45Z (GMT). No. of bitstreams: 1 DissRPC.pdf: 4541699 bytes, checksum: 0a15e746cc62d592608bcad54351b1db (MD5) Previous issue date: 2006-08-08 / The present study endeavours to contribute to a better understanding of the education in this country by means of a case study of the Centro de Divulgação Científica e Cultural CDCC (Centre for Scientific and Cultural Promotion). This centre was established in 1980 by the São Carlos campus of the University of São Paulo and since then put under the care of the Institute of Physics and Chemistry. The CDCC operates educational projects aimed at fostering scientific curiosity in basic educational level students. The investigation covers the process of CDCC s creation and seeks comprehension of its first motivation and objectives as well as peruses into the history of its building, which once hosted the Engineering School of USP-São Carlos. It does also investigate the services offered to the community, analyses CDCC administrative rules, and more incisively, reasons out the role of the Experimentoteca , the initial project that begot the Centre itself, and whose scope is to provide means of empirical experience of scientific theories for children at the basic level of education. The Experimentoteca is a portable laboratory of sciences that, under request, is taken to schools for classroom demonstrations. This project, initially restricted to São Carlos City and region, is currently extended to 31 cities of 13 different states. Following the steps of Buffa and Nosella, an epistemological frame of reference is taken from work and educational relations as well as from the relations of general overview and singular descriptions, as established by the New History, along with analysis of documents and facts under the educational viewpoint of the country. The sources are both the literature concerning community roles of the university, defined as one of the corners of the university s triple mainstay in the 5,540/68 Bill and the 1988 Constitution, and yet the literature concerning the history of Brazilian education, chiefly after the 5,692/71 Bill, which was in force when the CDCC was created. Additional research sources are magazines, books, scientific articles concerning the CDCC and its building, as well as CDCC s reports and governance rules. Interviews with CDCC s workers and founders and questionnaires applied to students using the Experimentoteca are yet complementary sources. Data analyses avail a conclusion that CDCC orientation differs from the patronizing stance that pervades most of community services. Indeed, evidence was produced as to suggest that CDCC s intervention fosters reflection and responsibility among students. Nevertheless, the scientific curiosity does not seem to blossom as expected. School and social-family adverse environments do not make room for such: these are children of low income working class parents, who are educationally deprived and subjected by a neglected educational policy that includes deteriorated buildings, unhealthy classrooms, and teachers discouraged by low wages and bad working conditions. The CDCC s work stands alike a clean drop over a polluted river but its initiative is not useless, and does meet its best meaning in the respect to citizenship and in the interchange of lay and academic wisdom provided by the collaboration between university and community. There remains a hope that such values that exceed school limits be dully appreciated by the country politicians. / A presente dissertação busca contribuir para o entendimento da educação no país através do estudo de caso do Centro de Divulgação Científica e Cultural (CDCC), um trabalho de extensão realizado, desde 1980, pela Universidade de São Paulo, câmpus São Carlos, sob responsabilidade do Instituto de Física e Química. Este Centro realiza projetos educacionais voltados a alunos do ensino básico com o intuito de desenvolver o interesse pelas ciências. A pesquisa percorre o processo de criação deste Centro e busca entender suas motivações e objetivos iniciais; resgatar o histórico do prédio no qual se instala, que foi a primeira sede da Escola de Engenharia da USP-São Carlos; analisar as atividades oferecidas à população; apreciar o seu regimento administrativo; e, de forma mais aprofundada, estudar o desenvolvimento do projeto Experimentoteca, mola propulsora para o nascimento do Centro, cujo objetivo é instrumentalizar o aluno do ensino básico para que ele entenda, através da prática, as teorias científicas aprendidas em sala de aula. A Experimentoteca é um laboratório de ciências circulante e os experimentos são levados às escolas que os solicitam para serem realizados em sala de aula. O projeto, que se iniciou em São Carlos e região, atualmente, é usado em 31 cidades de 13 Estados do país. Seguindo os passos de Buffa e Nosella, usam-se como referências teóricometodológicas as relações de trabalho e educação, as relações das visões gerais e descrições do singular estabelecidas na chamada Nova História, além da análise de documentos e fatos sob a ótica educacional do país. As fontes são tanto a bibliografia que se refere ao trabalho de extensão universitária, definido como um dos elementos do tripé de sustentação da universidade na Lei n° 5.540/68 e ratificado na Constituição de 1988, quanto a que analisa a história da educação brasileira, principalmente depois da Lei n° 5.692/71, que se encontrava em vigência no país à época da criação do CDCC. Também são fontes documentais da pesquisa: revistas, livros, artigos científicos sobre o CDCC e sobre prédio onde atua, relatórios das atividades, projetos e regimentos do Centro. Entrevistas gentilmente cedidas por funcionários e participantes da criação do CDCC são fontes orais fundamentais para a análise assim como entrevistas e questionários respondidos por alunos que utilizam a Experimentoteca. Da análise dos dados e informações obtidos pôde-se concluir que a orientação do Centro de Divulgação Científica e Cultural distingue-se da visão assistencialista que guia a maioria dos trabalhos de extensão. De fato, reuniram-se evidências que sugerem que a intervenção do CDCC promova reflexão e responsabilidade entre os alunos que seu trabalho alcança. No entanto, o esperado interesse pelas ciências é diluído em meio aos problemas que os estudantes da rede pública enfrentam em seu cotidiano tanto escolar quanto sócio-familiar. Eles são filhos de trabalhadores de renda modesta, de limitado capital cultural e ainda vítimas de uma política educacional deficiente que proporciona ensino em prédios mal cuidados, em salas mal ventiladas e com professores desmotivados por baixos salários e más condições de trabalho. O trabalho do CDCC acaba sendo uma gota de água limpa em um rio sujo, porém a iniciativa não é inócua e encontra seu maior significado no respeito ao cidadão, na troca entre os saberes popular e acadêmico, na abertura da comunicação da universidade com a população. Permanece a expectativa de que esta compreensão de que a educação excede os muros da escola ganhe o respeito que reclama dos governantes do país.

Esta tese discute potencialidades, limitações e desafios envolvidos na implementação da abordagem histórico-investigativa (HI) em aulas de física. Entendemos como abordagem histórico-investigativa, o uso de atividades experimentais de cunho investigativo pautadas na história e filosofia da ciência, centrada no aluno e orientada pelo professor, de modo a criar situações de ensino e aprendizagem que propiciem a aprendizagem de conteúdos científicos e metacientíficos e estimulem a argumentação em sala. A abordagem HI foi utilizada para criar novos roteiros para kits de calor, ótica e mecânica da Experimentoteca do Centro de Divulgação Científica e Cultural da Universidade de São Paulo (CDCC-USP localizado na cidade de São Carlos). Os novos roteiros foram desenvolvidos em parceria com professores usuários da Experimentoteca, atuantes na rede pública de ensino. A metodologia de pesquisa utilizada foi a Design Based Research (DBR) com o intuito de integrar a pesquisa com o desenvolvimento de intervenções educativas em ambientes de aprendizagem. Adotamos como referencial de análise das atividades aplicadas o Losango Didático, proposto por Méheut e Psillos, que considera as dimensões epistêmica e pedagógica dos saberes escolares. Também analisamos as Práticas Epistêmicas, propostas por Silva e por Araújo, que ocorrem ao longo das arestas do Losango Didático. / This thesis discusses the potentials, limitations, and challenges involved in the implementation of historical-investigative approach (HI) in physics classes. We understand as a historical-investigative approach, the use of investigative activities based on the history and philosophy of science, centered on the students and guided by the teacher. The main goals of the approach are to create teaching and learning situations that allow reflection on scientific and meta-scientific contents, to foster the learning of scientific concepts and the argumentation in class. The HI approach was used to create new guides for experimental kits on heat, optics, and mechanics of Experimetoteca of the Center for Scientific and Cultural Dissemination of University of São Paulo (CDCC-USP - located in the city of São Carlos). The new scripts were developed in partnership with public school teachers who are users of the Experimentoteca. The research methodology used was Design-Based Research (DBR) to integrate research with the development of educational interventions in learning environments. As framework for the analysis of the results, we adopted the Didactic Rhombus, proposed by Méheut and Psillos activities, which considers the epistemic and pedagogical dimensions of school knowledge. We also analyzed the Epistemic Practices, proposed by Silva and by Araújo, that occur along the edges of the Didactic Rhombus.

Submitted by Biblioteca do Instituto de Física (bif@ndc.uff.br) on 2017-05-26T18:58:18Z No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) dissertacao_MRCortes_vs final.pdf: 6401769 bytes, checksum: 5e83e87a68b85ac438726ec9e7a0ab44 (MD5) / Made available in DSpace on 2017-05-26T18:58:18Z (GMT). No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) dissertacao_MRCortes_vs final.pdf: 6401769 bytes, checksum: 5e83e87a68b85ac438726ec9e7a0ab44 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Esta dissertação é um estudo teórico de efeitos de canais acoplados em colisões de íons pesados, apresentando a descrição simplificada de um canal, e a mais realística de canais acoplados, realizamos uma investigação detalhada dos efeitos de acoplamento de canais em dois sistemas. O primeiro corresponde à colisão de um projétil esférico com um alvo fortemente deformado. Neste caso dinâmica de colisão é denominada pelos acoplamentos com os canais associados à banda rotacional do alvo. O segundo envolve um núcleo instável fracamente ligado, que apresenta um halo de próton. Neste caso, os efeitos de canais acoplados se devem ao acoplamento com o canal de breakup. Calculamos seções de choque de canais acoplados considerando os principais canais de reação de cada sistema, e comparamos os resultados com previsões da teoria mais simples de um canal. Calculamos também potenciais de polarização realísticos e e testamos sua validade no estudo do espalhamento elástico. / This thesis is a theoretical study of channel coupling effects in heavy ion collisions. We begin with a brief review of quantum theory of heavy ion scattering, considering the simplified single-channel description and the more realistic approach of the coupled channel method. The theories are then applied to two systems. The first corresponds to the collision of a spherical projectile with a highly deformed target. In this case the collision dynamics is dominated by the couplings with the channels associated with the rotational band of the target. The second system corresponds to collisions of an unstable weakly bound nucleus, which presents a proton-halo. In this case, the channel coupling effects are due to the breakup channel. In each case, we perform coupled channel calculations involving the most relevant channels, and compare the results to the predictions of the simpler single approach. We evaluate also realistic polarization potentials, and check their validities in studies of elastic scattering.

The structure of exotic nuclei is one of the main interests in current nuclear physics. Exotic nuclei present unusual properties, such as a low breakup energy, a short lifetime and/or a halo structure. Because of their short lifetimes, they can not be studied by usual spectroscopic techniques. Indeed, targets of such nuclei are impossible to build. But since the availability of radioactive beams, nuclear reactions have provided possibilities of exploring nuclei far from stability.<p><p>The investigation of exotic nuclei has been recently reactivated by the development of intense radioactive nuclear beams. As firstly observed for the deuteron, and then for other exotic projectiles such as $^6$He and $^{11}$Be, the internal structures of the interacting nuclei can have a significant effect on the elastic cross sections. Due to their low binding energy, the projectile dissociation process, leaving the target in its ground state, highly affects elastic cross sections but also other measurements such as transfer and fusion reactions. Accurate reaction theories are therefore needed. The coupled discretized-continuum channel (CDCC) method is one of those theories and assumes a projectile made of N clusters (usually N=2 or 3) impinging on a target which is structureless. The N+1-body Schrödinger equation is approximately solved by expanding the total wave function over the bound and continuum states of the projectile. These latter take into account the dissociation events and are approximately described by a truncated set of square-integrable wave functions. There are two available methods for discretizing the continuum, the pseudostate method where the projectile Hamiltonian is diagonalized within a finite basis of square-integrable functions, or the bin method where exact scattering wave functions of the projectile are averaged over bins in a finite region of space. In both cases, the N+1-body Schrödinger equation is replaced by a set of coupled-channel differential equations, which provides the physical quantities such as the collision matrix. In principle, the CDCC method can be very close to the exact N+1-body wave function and is adapted to low as well as to high energy reactions. However, its main interest consists in the low-energy domain.<p><p>In the present work, we propose a new approach to solve the CDCC equations. This method is based on the R-matrix theory associated with a Lagrange mesh basis. We will show that the combination of both approaches provides a fast and accurate technique to solve the CDCC equations, even for large systems, where traditional methods meet convergence problems. Before investigating collisions with exotic projectiles, we restrict ourselves to the simplest nucleus, the deuteron. Then we make a step towards a more complicated system, the $^6$Li which is a well known stable nucleus. We apply the CDCC method to the d + $^{58}$Ni and $^6$Li + $^{40}$Ca elastic scattering and breakup. These systems are considered in the literature as test cases. They have been investigated by several authors who showed the importance of the breakup channels in the elastic cross sections.<p><p>After having validated the present version of the CDCC method, we focus on $^{11}$Be, a typical example of a halo nucleus, with low binding energy and large quadrupole moment. Elastic, inelastic and breakup cross sections are computed in the CDCC formalism, at energies near the Coulomb barrier, where continuum effects in the scattering of exotic nuclei, and more specifically on the $^{11}$Be + $^{64}$Zn scattering, are observed. We show that converged cross sections need high angular momenta as well as large excitation energies in the wave functions of the projectile.<p><p>A Borromean nucleus is made of three constituents which are weakly linked together, but where each pair of those three constituents does not form a bound system. The name "Borromean" comes from the Borromean rings where, if any one of three rings is removed, the remaining two become unbound. Collisions with $^6$He and $^9$Be Borromean projectiles are studied in the present work. Again we compare our method with the $^6$He + $^{208}$Pb and $^6$He + $^{12}$C benchmark calculations. Afterwards, the convergence against the parameters of the description of the $^9$Be projectile is tested for the elastic cross section. The sensitivity to the technique employed to remove the forbidden states and also the sensitivity to the collision energy are investigated. / Doctorat en Sciences de l'ingénieur / info:eu-repo/semantics/nonPublished

One-nucleon halo nuclei are exotic nuclei which can be seen as a core around which orbits a loosely-bound valence nucleon. They are usually studied through reactions such as elastic scattering and breakup. The ratio method has been developed as a tool to study one-neutron halo nuclei at high energies. It consists of the ratio of angular cross sections, breakup and elastic scattering, which removes most of the sensitivity to the reaction mechanism and to the reaction model. In the simple recoil excitation and breakup (REB) model, the ratio simplifies to a form factor dependent solely on the wave function of the projectile. By measuring this observable and comparing it to the REB form factor, i.e. in the ratio method, more detailed information on the structure of the halo could be obtained. For neutron-halo nuclei at high energy, the ratio observable obtained from accurate CDCC and DEA theoretical calculations follows its REB prediction. I study the extension of this method to lower energies of the reaction which could make the measurement appropriate to facilities such as SPIRAL2 (GANIL, Caen, France) and ReA12 at FRIB (Michigan State University) and to proton halos. This is done by comparing the REB form factor to dynamical calculations of the ratio. The reactions investigated are the reaction of 11Be, the archetypical one-neutron halo nucleus, on 12C, 40Ca and 208Pb targets at 20 MeV/nucleon and of 8B, the archetypical one-proton halo nucleus, on 12C, 58Ni and 208Pb targets at44 MeV/nucleon.For these reactions, the adiabatic assumption is no longer valid due to the effect of the Coulomb interaction. This effect is mainly visible at forward angle for 11Be and is aggravated for 8B by the fact that the halo is charged. The ratio works less well than for neutron-halos at intermediate and high energies. Nevertheless, the ratio is shown to be very sensitive to the orbital angular momentum l0 in which the halo is bound and its binding energy E0, i.e. the single-particle structure of the projectile. Variations of l0 and E0 induce visible changes in shape and in magnitude (up to several orders) of the ratio. Also, the agreement of the ratio with its REB prediction is best when the projectile is loosely-bound and for low l0, i.e. for s and p waves. The validity of the method is not affected by the use of energy ranges—or bins— in the projectile continuum. These tend to increase the cross section without changing the agreement of the ratio with its REB prediction. The applicability of the method is finally explored at high energy for proton-rich nuclei 17F, 25Al and 27P. I show that the ratio method works the latter since this nucleus is bound by a mere 0.870 MeV in the s-wave. For the other nuclei, although the agreement of the ratio with its REB prediction is less good than for neutron-halo nuclei at high energy, it still provides estimates of nuclear-structure features, such as l0 and E0 and could be applied in what can be called an approximate application of the ratio method. Heavy nuclei exhibit a neutron skin, i.e. a thin layer around the nucleus where only neutrons are found. The thickness of the skin is highly correlated with the slope of the symmetry energy. The process of coherent neutral-pion photoproduction is used to extract the nuclear density and hence the neutron-skin thickness of heavy nuclei. In order to analyse recent data on the photoproduction on 12C, 40,48Ca, 116, 120, 124Sn and 208Pb, I build a reaction code. My model uses the formalism of Kerman, McManus and Thaler (KMT) which allows to build the photoproduction matrix on a nucleus from the ones describing the elementary process on a single nucleon. Within the impulse approximation, the photoproduction is seen as the coherent sum of the photoproduction on each of the nucleons. In the plane wave impulse approximation (PWIA), no rescattering of the pion is considered after its production and the cross section is directly proportional to the Fourier transform of the density. Such process is taken into account at the distorted wave impulse approximation (DWIA) by considering a potential simulating the pion-nucleus interaction and built from the KMT formalism.The agreement of my model with the data is good, especially for 208Pb. The distortion has a significant impact on the photoproduction process. The sensitivity of the process to the density of the target is analysed by performing the calculations with several different densities calculated in different structure models. The distortion has the effect of deteriorating this sensitivity. In the particular case of a 208Pb target, the impact of variations of the neutron-skin thickness of around 0.1 fm on the photoproduction cross section is ten times smaller than the size of the error bars on the experimental data. These results, although less dramatic, hold for the tin targets, for which preliminary data exists. In the light of these results, the coherent neutral-pion photoproduction process does not seem to be suited in the study of the neutron-skin thickness. This conclusion goes in contrast to the results of recent measurements on 208Pb, for which the method was shown to be sensitive to fine details of the density. / Doctorat en Sciences de l'ingénieur et technologie / info:eu-repo/semantics/nonPublished